diff --git a/src/main.c b/src/main.c
index 183076b..0105a42 100644
--- a/src/main.c
+++ b/src/main.c
@@ -223,10 +223,51 @@ fail:
     return result;
 }
 
+bool preprocess_file(const char* file_path, char** result) {
+    char command[256] = {0};
+    sprintf(command, "gcc -E %s", file_path);
+
+    FILE* fp = popen(command, "r");
+    if (fp == NULL) {
+        fprintf(stderr, "ERROR: Failed to run command: %s\n", strerror(errno));
+        return false;
+    }
+
+    char line[512];
+    size_t line_num = 0;
+    char file_name[512];
+
+    // TODO: use dynamic array instead
+    size_t cursor = 0;
+    *result = (char*) malloc(2048 * sizeof(char));
+
+    bool collecting_content = false;
+
+    while (fgets(line, sizeof(line), fp) != NULL) {
+        if (sscanf(line, "# %zu \"%s\"", &line_num, file_name) == 2) {
+            // remove trailing "
+            file_name[strlen(file_name) - 1] = '\0';
+
+            if (strcmp(file_name, file_path) == 0) {
+                collecting_content = true;
+                continue;;
+            }
+        } else if(collecting_content) {
+            size_t line_len = strlen(line);
+            memcpy(*result + cursor, line, line_len);
+            cursor += line_len;
+        }
+    }
+
+    pclose(fp);
+
+    return true;
+}
+
 int main(int argc, char** argv)
 {
     const char* program_name = argv[0];
-    if(argc == 1) {
+    if (argc == 1) {
         fprintf(stderr, "ERROR: missing required argument <input_file>\n");
         fprintf(stderr, "Usage: %s <input_file>\n", program_name);
         return 1;
@@ -234,7 +275,7 @@ int main(int argc, char** argv)
 
     // read input file
     char* input_content;
-    if(!read_entire_file(argv[1], &input_content)) return 1;
+    if (!preprocess_file(argv[1], &input_content)) return 1;
 
     // init lexer
     char string_store[1024];